﻿ ﻿Commonly Used Symbols - Mathematical Composition

# Commonly Used SymbolsMathematical Composition

Use mathematical symbols in running text only if they are presented with a numerical value within parentheses. These symbols can be used in figures, tables, and boxes with no explanatory footnotes. Some commonly used symbols are as follows:

 Symbol Description > greater than ≥ greater than or equal to < less than ≤ less than or equal to ± plus or minus (This symbol should not be used to indicate variability around a central tendency, eg, “The control group had a mean [SD] value of 12 ,” not “The control group had a mean of 12 ± 7.”) integral from value of a to value of b summation from a = 1 to a = 30 product of a = 1 to a = 30 Δ delta (change, difference between values) f function ≠ not equal to ≈ approximately equal to ∼ similar to (reserve for use in geometry and calculus, when it can be used in equations to mean “is distributed as”; use words in other cases where “approximately” is meant) ≅ congruent to ≡ defined as ∴ therefore ∞ infinity ! factorial, eg, n! = n(n − 1) (n − 2) . . .  1

The following symbols are usually reserved for specific values:

 π pi (approximately 3.1416; do not confuse with uppercase Π) e base of the system of natural logarithms (approximately 2.7183; see 20.3.3, Logarithmic Expressions; in statistical equations, however, “e” represents the error term in a regression equation) i the square root of −1

For a list of additional symbols that are used in statistics, see 19.6, Statistical Symbols and Abbreviations.

The following are examples of these commonly used mathematical expressions:

>105 CFUs/mL

24.5 ± 0.5

L ≈ 2 × 1010 m

f (x) =  x + Δx

y = dx/dt

P < .001

P < 10 × 3—10 (for very small P values, do not use “e” to represent the exponent; see 19.4.2, Rounding)   r ! (n − r)!

(ex + e−x)/2

Y = β1 + β2 + e

kg ⋅ m ⋅ s−2  (in this case the operation sign is indicated on both sides of the ellipses)

Any symbols rendered in HTML should be compatible across most commonly used browser platforms.

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